Probabilistic design and management of environmentally sustainable repair and rehabilitation of reinforced concrete structures Michael D. Lepech a,⇑ , Mette Geiker b , Henrik Stang c a Department of Civil and Environmental Engineering, Stanford University, Room 285B, Yang and Yamazaki Energy and Environment Building, Stanford, CA 94305-4020, USA b Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway c Department of Civil Engineering, Technical University of Denmark, Lyngby, Denmark article info Article history: Received 15 October 2012 Received in revised form 27 June 2013 Accepted 9 October 2013 Available online 17 October 2013 Keywords: Sustainability design Life cycle assessment Service life Concrete repair Life cycle management abstract This paper presents a probabilistic sustainability design framework for the design of concrete repairs and rehabilitations intended to achieve targeted improvements in quantitative sustainability indicators. The framework consists of service life prediction models combining deterioration mechanisms with limit states and life cycle assessment models for measuring the impact of a repair or rehabilitation. Both types of models (service life or LCA) are formulated stochastically so that the time to repair and the accumulated sustainability impact are described by probability density functions. This leads to a proba- bilistic calculation of cumulative impacts throughout the structure’s service life, from initial repair to functional obsolescence (end of life). The methods discussed are in accordance with sustainability design requirements within the 2010 fib Model Code. A case study is presented which computes the probability that reinforced concrete repair strategies using thicker concrete cover will meet future greenhouse gas emission reduction targets proposed by the UN Intergovernmental Panel on Climate Change. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction In 1992, the United Nations Framework Convention on Climate Change was adopted to ‘‘stabilize greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate’’ and scientists recommended capping atmo- spheric CO 2 concentrations below 550 ppm [1]. For large societal systems, such as transportation and energy production, many strategies have been proposed to meet these goals in the next 50 years including widespread adoption of nuclear energy, drastic reductions in automobile fuel consumption, and geologic carbon sequestration [2]. Comprising a major part of these strategies, civil infrastructure built of reinforced concrete lies at the nexus of two major sustainability challenges; emissions from transportation and construction materials, in particular, cement production. Transpor- tation comprises 30% of US CO 2 emissions [3], while Portland ce- ment production emits approximately 5% of global anthropogenic CO 2 emissions [4]. Collectively, the design, operation, maintenance, rehabilitation, and retirement of reinforced concrete transporta- tion infrastructure, and concrete structures at a whole, represent a large opportunity and challenge in realizing the United Nations’ vision of sustainable development. Recognizing this opportunity, frameworks and guidelines have been introduced to aid transportation planners and structural engineers in the design and management of more sustainable infrastructure. It is helpful to classify these into three subsets as proposed by Gowri [5]; (1) knowledge-based methods, (2) rating schema, and (3) performance-based tools. It is also useful to distinguish among approaches that are regional, local, or project specific. Knowledge-based tools are manuals, guidelines, and deemed-to-satisfy design recommendations including, for exam- ple, Green Playbook [6] in the US, and the Green Infrastructure Planning Guide [7] in the EU. These approaches can span from re- gional guidelines for greenspace management to project-specific design recommendations. The second subset, rating schema, in- cludes design checklists, frameworks, and calculators used to quantify an infrastructure’s sustainability profile. There are a num- ber of infrastructure rating systems currently in use including CEEQUAL [8] in the UK, Greenroads [9] in Washington State in the US, I-LAST [10] in Illinois State in the US, GreenLITES [11] in New York State in the US, the Australian Green Infrastructure Council Rating Tool [12], LEED for Neighborhood Development (ND) [13] in the US, BREEAM Communities [14] in the UK, and CAS- BEE Urban Development (UD) [15] in Japan. Similar to guidelines and recommendations, these range from regional to project-spe- cific in scope. The third subset, performance-based tools, include life cycle assessment methods and material flow analyses, along with performance simulation tools for calculating total energy 0958-9465/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cemconcomp.2013.10.009 ⇑ Corresponding author. Tel.: +1 650 724 9459; fax: +1 650 723 7514. E-mail address: mlepech@stanford.edu (M.D. Lepech). Cement & Concrete Composites 47 (2014) 19–31 Contents lists available at ScienceDirect Cement & Concrete Composites journal homepage: www.elsevier.com/locate/cemconcomp